3D Sound and Digital Cables - Why your games are in stereo only

Discussion in 'PC Audio' started by rawhide, Oct 25, 2005.

  1. rawhide

    rawhide Member

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    So you've got a sound card or motherboard with either a coaxial or optical digital-out plug. You've connected it to your fancy speakers or home theatre receiver, but something's not quite right... have you noticed that you hear sounds from your favourite 3D games in the front speakers only, or you hear the same stereo sounds from all 4, 5, 6 or 7.1 speakers?

    Well my friend, you've just fallen into possibly the most common trapping of PC digital sound...

    First, a little technical info. I won't spend too much time on the fine details, I'll try and sum it up as best as I can.

    Analogue vs. Digital: Analogue sound travels as waves of electricity that are subject to interference from nearby electronic equipment. Digital overcomes this by encoding the sound into zeros and ones before sending it over the cables, much like the screech of an old modem when you pick up the phone (we don't understand it, but computers can process it). Digital is tolerant to interference, but excessive interference will stop the sound entirely, you either get a perfect signal or none at all.

    Digital Formats: When audio is encoded digitally, the equipment at both ends needs to be able to recognise the codes of zeros and ones. That means talking in the same "language", also known as "format" or "standard". There are more, but only three digital formats are in mainstream home sound use. Those being PCM, DTS and Dolby Digital (also known as AC3). For more detailed information on sound formats, try this thread on the Audio Visual forum.

    Encode and Decode: In the context of this thread, these two terms relate to converting sounds to and from a digital signal. Your sound card ENCODEs a digital signal in one of the above formats, while the speaker system (or home theatre receiver) at the other end DECODEs that signal.


    Anyway, on with the story...

    The digital format is really where this problem lies. Your sound card is sending your game's sound in PCM format, and chances are there's nothing you can do about it.

    Every sound card with a digital plug is able to encode PCM. PCM is uncompressed, it's fast, simple and cheap to encode and used in everything from old digital telephone systems, to Compact Discs (Wikipedia). The PCM format supports 2 channels of sound only, that is, stereo. When you play a game on your computer, your sound card is still making a PCM signal and sending that over the digital cable, so you will only ever get LEFT and RIGHT.

    I'll just repeat that last point by itself for emphasis...

    When you play a game on your computer, your sound card is still making a PCM signal and sending that over the digital cable, so you will only ever get LEFT and RIGHT.

    Right about now, some of you reading this will be thinking something like "but when I play a DVD on my computer I get my surround sound just fine", and you're correct. In this case the people producing the DVD have already ENCODEd either a DTS or Dolby Digital (AC3) signal and stored it on the DVD. Your sound card is simply copying that signal and sending it straight over the digital cable without doing any processing of its own (the same applies to HDTV cards I think, except the AC3 signal is coming, already encoded, from the television broadcast).

    So, what can you do about it?

    Well, sorry folks, but the only way you're going to get proper surround sound from your 3D games with your current sound card is to hook up your speakers using all those seperate analogue plugs you probably have at the back of your computer.

    There are alternative solutions however...

    • The nForce2 motherboard chipset with "Soundstorm" on-board sound has a feature that allows it to ENCODE 3D game sound into a Dolby Digital signal on-the-fly, instead of relying on PCM stereo
    • The HDA Digital X-Mystique 7.1 sound card (plugs into any standard PCI slot) also has a similar feature, but comes with the advantage of not being a number of years out of date
    • Creative have a product called the Home Theater Connect DTS-610, which allows you to encode six channels of analogue sound into a DTS signal on the fly, however this means you still have to run a bunch of analogue cables from your PC sound card to the DTS-610 box, and then run a digital cable from that to your speakers / hifi

    Well I hope that dispells some misconceptions that people have and helps you judge which product to buy. I'll open the floor to corrections, suggestions and more in-depth discussion, but wanted to try and keep this first post as simple as possible without losing too much useful info. I haven't even spell / grammar checked it yet :D

    Something like this should be stickied here IMHO. If not this post specifically, then I hope I've at least given something that others can link to and say 'here, read this'.
     
    Last edited by a moderator: May 17, 2009
  2. skyline34

    skyline34 Member

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    Nice write up. If only i had of read this 4 days ago. When i was pulling my hair out trying to get my onboard ac97 sound card to output 5.1 sound through coax !

    I have since done some reading and figured out what you have said in your thread, and dropped some coin on an X-Mystique.

    /rant
    Its got me wondering why more companys (hello creative) don't include these sorts of features, especially when you pay hard earned cash for gimmiky buzz words like EAX 2 3 5 703247 whatever bloody number they tag on the end. Obviously they don't think the market wants this sort of thing. I have always had a soft spot for creative since i purchased my SB live value about 3 years back. But i am slowly losing every bit of respect i ever had for them.
    /end rant
     
    Last edited by a moderator: May 17, 2009
  3. $qwuzzy

    $qwuzzy Member

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    nice work rawhide - maybe sticky?


    it's creative.........nuff said

    see here is your mistake - but it's good to hear that you're learning from it.
     
  4. chicken-

    chicken- Member

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    Creative's Answer is probably the worst way of solving the spdif surround problem I can imagine. Having your output go through so many ADC/DACs before actually reaching your speakers cannot be good no matter how high quality their processing is. Not to mention still requiring the 5.1 analog cables to run out of your soundcard, which defeates the entire purpose of using a single digital connection.
     
    Last edited: Oct 26, 2005
  5. OP
    OP
    rawhide

    rawhide Member

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    Thanks guys.

    :thumbup:

    Yep, the previous excuse was that it was too expensive to license Dolby / DTS tech for mass production, and that nVidia could only put it on their motherboards because of the Xbox deal with Microsoft. But if that was truly the case these days, how did HDA manage to put it on an affordable card? Either times have changed and that excuse is no longer valid, or HDA are getting around the license issue somehow. :leet:

    Same. Haven't owned a Creative card since the AWE-32 (back when midi music was still in use, it sounded great). When Creative killed Aureal and essentially silenced their tech (I had an Aureal card with A3D2 at the time), I lost all respect for them. I was on the verge of buying an Audigy 2 ZS recently because my current card was dying and running an nForce2 mobo was out of the question, and then I found the HDA, and all was good.

    Couldn't agree more. I can certainly see it having some application for someone looking for a cheap digital encoder, like maybe someone running a backyard video production room, but it's definitely a complete waste of time and money for use with PC audio.

    Anyway, I guess this thread shouldn't really turn into an all out Creative-bash, but it could be argued that it's quite on-topic, since they're a big reason behind "why your games are in stereo only" :lol:
     
  6. chicken-

    chicken- Member

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    My theory on the Dolby License, is that with NVidia Soundstorm all but gone, Dolby were in need of someone to make use of Dolby Live, and therefore licensed it to CMedia for a significant discount. This also ment that they had Dolby encoding hardware back out there on sale, just in time to beat DTS's own entry into the PC encoding market. (although strange because DTS also partnered with CMedia to make their first encoding chip. :Pirate: )

    Since Creative had previously ignored Dolby Live, it's unlikely that Dolby would now give them any discount similar to CMedia's, which is why Creative have gone with the DTS alternative encoder in the DTS-610.
     
  7. KLoNe

    KLoNe Member

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    HDA should be turning up tomorrow :D

    That's a terrific guide rawhide. I call sticky!
     
    Last edited: Oct 26, 2005
  8. slayer

    slayer Member

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    A good write up! :)

    A couple of quick questions, On my receiver (denon 2805) it only receives a PCM stereo signal from my Chaintech AV710 (via optical cable) when playing Quake4. I've noticed in the menu's it has settings for surround sound but they are greyed out for my card with something about openAL (is this a new format?) Is there any chance of enabling these settings or does this require a different card all together.

    Failing that what is the difference between these cards that create a 5.1 signal from the original PCM source and me just pressing something like dolby pro logic II or dts emulation on the amp which will then output the original 2 channel pcm signal into a 5.1 signal? I'm just trying to get my head around it because as far as I can tell in cases like these neither of them have an original 5.1 track to work with so they both have to do a certain ammount of guesswork on where to send sounds?

    hope that makes some sense

    thanks in advance
     
    Last edited: Oct 27, 2005
  9. OP
    OP
    rawhide

    rawhide Member

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    Slayer,

    I don't know about your sound card in Quake 4 specifically. You'll need to check with the manufacturer of either the card or the chipset it uses to see if it supports OpenAL. Check the advanced settings of your speakers in Windows itself to see if it's set to stereo or 5.1 speakers.

    FWIW - The HDA X-Mystique doesn't support OpenAL either (yet), but the surround sound works.

    As for the difference, the cards that create a 5.1 digital signal do just that, they don't actually create it from any original PCM source, there's no PCM signal to begin with in their case. They're just able to make a 5.1 signal instead of a PCM (stereo) signal. Though, for music purposes, you can usually tell them to switch back to a PCM signal for higher (uncompressed) quality.

    When you enable PLII or DTS emulation on your Denon receiver, it (the Denon) is processing the stereo signal and faking the surround channels. Like, picking out voice-like frequencies and sending them to the center speaker, and so on. Well, that's the gist of it anyway, check Wikipedia or Google for more info on pro logic I guess.
     
    Last edited: Oct 27, 2005
  10. HaZZaD

    HaZZaD Member

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    Do these same rules apply to xvid files encoded with a DD soundtrack(2.0 or 5.1)? I can get 5.1 out of a dvd on my board, but cannot get any xvid files to playback in 5.1. Nor can I get my digital TV application to output in 5.1, though i suspect that has more to do with the DTV software in use that anything else.

    HaZ
     
  11. OP
    OP
    rawhide

    rawhide Member

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    You're probably right about it being the software.

    For movie files (such as AVI files) with an AC3 soundtrack it requires a player that knows to pass the signal through to the digital plug. When in doubt with movies, give VLC media player a try - http://www.videolan.org/vlc/ - it'll usually play any file you throw at it. I can load up an xvid with a 5.1 dolby soundtrack and go (in vlc) Audio -> Audio Device -> A/52 over S/PDIF. In this case, if it's running properly, you'll find the volume and equaliser settings on your PC don't do anything, because it's passing the sound directly to your processor.

    Can't help you with DTV though, but yes it's probably the software. I plan on getting an HD tuner car for my PC sometime soon so maybe I can flesh this out a little when the time is right.
     
  12. FuNkY MoOsE

    FuNkY MoOsE Member

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    In the process of self educating myself on this topic I found a heap more 'alternative' solutions.

    Nice list of Dolby Digital Motherboards on htpcnews (There's even a couple of a64 mobos there as well as a heap of intel stuff)

    The X-plosion and X-mystique that're covered pretty heavily in these forums. Reading around I saw a couple of unconfirmed sources say that the X-raider wouldn't be round till Q4 this year. =\

    The aureon from terratec which is painfully expensive compared to everything else.

    The Montego‚ĄĘDDL from Turtle Beach which is pretty pointless because I can't seem to find a Australian vendor for. I think this also uses the same chip as the x-mystic and costs a fare bit more, not really worth the effort.

    The Diamond XtremeSound 7.1 DDL is interesting, but it essentially seems to be identicle to the Xmystique for a slightly smaller price if you can even get one in Australia. I dunno if this card would suffer from the same problems the X-mystique does, but it would apear to use the same drivers so it probably does.

    Also of note, is that most of the on board Dolby Digital Live stuff is done through software encoding which puts a bit of extra load on the cpu, at least most of the intel stuff is. I have no idea what they're using on the couple of AMD boards.

    So the short of it is, the X-Plosion seems to be pretty much in a class of its own. And the X-Mystic seems to be pretty much the only realistic option for its price in Australia, although there are similar cards based on the same chip starting to apear overseas that could be cheaper (noteably the diamond card).

    This is just information I dug up while trying to find a useable replacement for my nforce2 soundstorm system.
     
  13. GOATMAN!!!

    GOATMAN!!! Member

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    so later nvidia chipsets (Nforce3&4) don't have this feature???


    My "nvmixer" panel says about soundstorm in its about panel. Well, it says they are a trademark of nvidia anyway. Seems odd that they would take this feature out?

    Bugger. I hate it when I downgrade like this :(

    Pity my old asus anz8x-deluxe died :(
     
    Last edited: Jun 20, 2006
  14. MrRand0m

    MrRand0m Member

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    So in other words.... if your a gamer and have a nice audigy card - forget about getting a $400 set of digital speakers.

    What a crock - talk about a load of bullshit. Glad I read this.

    When I want to upgrade, I think i'l stick to an audigy 4 and standard 7.1 surround sound setup. Currently running an Audigy with a creative 5.1 setup and it does the job resonably well.
     
  15. VZey

    VZey Member

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    wow guys thanks I was going to get a digital cable for my new z5500's but now I won't bother, I'll just stick with analogue.
     
  16. imgod22222

    imgod22222 Member

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    Does this mean that mp3 files should be able to give surround sound? After searching, this is what I found out.

    MP3 is a compression format. It provides a representation of pulse-code modulation-encoded (PCM) audio data...
    Source: http://en.wikipedia.org/wiki/MP3

    I have a couple of mp3 tracks that were ripped from a 7.1 audio DVD and only play through 2 speakers. I have 5.1 speakers connected to my karajan onboard audio. Why isn't it playing through all 5.1 speakers?
     
  17. Hung-Two

    Hung-Two Member

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    What encoder and encoding settings were used? I'm not sure if any mp3 encoder has the option of encoding more than a stereo audio stream.
     
  18. imgod22222

    imgod22222 Member

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    /..\ I'm sorry to say, but I don't know. I'll start a new thread so as not to hijack this one, with a slightly different topic.
     
  19. Jedi Jezz

    Jedi Jezz Member

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    Three cheers for nforce 2 sounstorm! The only reason why I still use an athlon xp-m setup as my gaming box and another setup for my tv.
     
  20. aerospyke

    aerospyke Member

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    I have the X-plosion and will either get the 5500's or klipsch promedia 5.1's ... can't decide which. ..

    until i decide i'm stick with a stereo lead going to my 5.1 stereo (it sucks, stereo is 5.1, audio source is 5.1 but transmission medium is not and the stereo doesn't have any input besides stereo. :unhappy face:
     

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